When an infusion, blood collection, or administration of a drug solution is performed on a patient, a medical needle body such as a hollow injection needle is used. The needle body is discarded after use. However, if the used needle body is discarded as is, a disposal worker or the like may possibly experience an accident, where the needle tip is erroneously stuck into the worker's finger or the like. In particular, since blood adheres to and is left on the front surface of the needle body, or on an inside portion thereof, such erroneous sticking may possibly lead to infection.
To prevent erroneous sticks, measures are taken to cap and discard the used needle body under existing circumstances. However, also when work is performed for capping the needle body, the worker must pay close attention in order to prevent the needle tip from being stuck into his or her hand. This poses a problem in that disposal of needle bodies after use requires thousands of man-hours.
To eliminate such a problem, a protector has been proposed, which can safely cover the needle tip of a needle body after use. Specifically, the protector is mounted onto a middle portion of the needle body during use of the needle body, and after use, the protector is shifted to and covers the needle tip. (See, e.g., Patent Document 1.)
The protector described in Patent Document 1 has a plate-like protector body made of a metal material. The protector main body includes a first section formed with a first hole, which is adapted to receive a needle body with a generally uniform outer diameter when the needle body is passed therethrough, a second section formed with a second hole, and a third section that connects one end of the first section to the second section. The protector is configured in the following manner. Namely, while the protector covers a needle tip, a frictional force is generated or increased between the inner circumferential surface of the first hole and the outer circumferential surface of the needle body, in order to stop the protector relative to the needle body.
However, with the protector described in Patent Document 1, the inner diameter of the first hole may be excessively greater than the outer diameter of the needle body depending on, e.g., the machining accuracy of the first hole. In such a case, the outer circumferential surface of the needle body virtually does not come into contact with the inner circumferential surface of the first hole. In other words, the frictional force virtually is not generated between the outer circumferential surface of the needle body and the inner circumferential surface of the first hole. Consequently, it is likely that the protector may become disengaged from the needle body.
To solve this problem, using a different-diameter needle as a needle body has been proposed. Such a different-diameter needle is one that includes an elongate main needle body with an enlarged-diameter section provided on the distal side of the main needle body, and having an outer diameter greater than that of the main needle body. For using the different-diameter needle, while the protector covers the needle tip, the enlarged-diameter section comes into abutment against a circumferential edge of the first hole, so that the protector is stopped with respect to the needle body.
However, even if such a different-diameter needle is used, pulling (or shifting) of the needle body may occur and excessively pull the needle, thereby allowing the enlarged-diameter section to press and deform the circumferential edge of the first hole, which increases the inner diameter of the first hole. Thus, it is possible that the enlarged-diameter section may pass through the first hole, so that the protector may become disengaged from the needle body.
With the protector described in Patent Document 1, when an operation for pulling the needle body is executed, the needle body may in some cases become slanted relative to the operating direction. Thus, when the needle becomes caught by the circumferential edge of the first hole, the needle body shifts and increases sliding resistance, thereby making it hard to execute the pulling operation.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-154364